| As one kind of heavy metal toxicant, the cadmium can cause acute and chronic poisoning. It is also known to be a carcinogenic, teratogenic and mutagentic element. But the main hazard of cadmium is the chronic poisoning caused by cumulative cadmium in human body. The cadmium in human body is mainly absorbed from food contaminated by cadmium existed in environmental pollution. In order to prevent and reduce the hazard of cadmium, monitoring the content of cadmium in environment, food and food packages is an important strategy for limiting cadmium intake by human body. Many methods have been established for the determination of cadmium such as spectrophotometry, atomic absorption spectroscopy (AAS), anodic stripping voltammetry (ASV), cathodic stripping voltammetry (CSV), liquid chromatography (LC), gas chromatography (GC), inductively coupled plasma emission spectroscopy (ICP) and so on.But the above mentioned methods have some shortcomings. For example, some methods yield good sensitivity and selectivity, but require costly instruments and professional manipulators. If we can prepare a kind of test strip for the fast qualitative or semi-quantitative determination of cadmium in food, we can confirm that whether the level of cadmium in food is accord with the demand of the relevant standard in a short time. This method would be very practical in the work of cadmium contamination monitoring. However, there is no document about detecting cadmium in food using test strip at present. Because the content of cadmium in food is very low, it's very difficult for us to detect it using test strip.Based on the reaction of cadion and the cadmium with the spectrophotometric detection, a fast detecting method for cadmium in food was established. The main results and conclusions were listed as the following:1. The filter paper soaked by the cadion solution of KOH-C2H5OH, an intensity orange color displayed after reaction with cadmium, it suggests that there is possibility for using test strip to detect the cadmium.2.Further study, We found that the test strip, which was prepared with the cadion solution(0.1%), could develop the most obvious color grade when it was reacted with the neutral solution, and the reaction completed immediately and didn't need heating or extraction. Due to the low residue, little impurity, the quantitative filter had the best color grade. So it was used as the carrier of cadion for the determination.3.The test strip was kept in different temperature (-18℃, 4℃ , 45℃) for 6 hours respectively. The reaction results had no difference from those of the test strip kept under room temperature. It suggests that the test strip can be used at wide range of temperature.4.In order to study the potential interference of various interfering substances on the reaction color grade, an interfering experimence was conducted. We found that the substances of Mn2+, Cu2+ and Zn2+ can be tolerated up 50~100 folds to the cadmium, but the substances of Mg2+, Ca 2+, Hg2+, Pb2+, Fe3+, Ag+ have a little interference on the color grade, fortunately, the compound testudo can obviously reduce the interference except Pb2+.5.Under these conditions, a linear concentration range between 0-10 mg/L was obtained, and the detection limit was 1.0 mg/L.In this paper, we established a kind of test strip for the determination of cadmium in food. It has the advantages of good sensitivity, convenient, and can tolerate other interfere substance. If it is used in combination with reflector apparatus, the error of range estimation would be reduced.The test strip can be used successfully for the detection of cadmium in food, as well as in waste water sample and in soil sample with satisfactory results. |
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